Switched Capacitor (SC) regulators can be used in various applications including direct-current-to-direct-current (DC/DC) converters and battery charger integrated circuits (ICs).
It can be helpful to measure the output current of a Switched Capacitor (SC) regulator. For example, it can be helpful to measure the output current of an SC battery charger IC so that the SC battery charger IC can regulate a charge current used to charge a battery. To regulate the charge current, the charger IC needs to measure its output current and determine if it is larger or smaller than a target output current value. Based on that result, the charger IC can adjust the output current to be as similar as possible to the target value. In another example, it can be helpful to measure output power in a SC DC/DC converter by measuring output current and multiplying it by an output voltage. In a power management IC (PMIC) with multiple SC DC/DC converters, it can be helpful to measure the output power of each SC DC/DC converter so that the PMIC can keep track of how much power is consumed by each DC/DC converter.
While it is useful to measure output current, prior techniques for doing so are inefficient from a power usage perspective. A straightforward way to measure output current is to add a series resistor at the output and measure the voltage across the resistor as illustrated in FIG. 1. Since IR=V, measuring the voltage across the resistor RSERIES 120 and dividing by the resistor value can compute the amount of current flowing through RSERIES 120. The problem with this approach is that there is power loss of I2R. If R is equal to 5 milliOhms and I is equal to 5 Amps, I2R power loss is equal to 125 milliWatts. It is possible to reduce R to reduce I2R loss. However, a small R value results in a small IR=V value, and it becomes more difficult to sense the small voltage value (e.g., a higher bit analog to digital converter is needed to sense smaller voltages).
Accordingly, new mechanisms (which can include circuits and methods) for measuring the output current of a switched capacitor (SC) regulator are desirable.